Insulation of wire



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m. W m5 p ma wm Mm ma YAM B .Mz c .n v Z. 4 d a Patented Aug. 9, 1932 UNITED STATES PATENT OFFICE RALPH RUSSELL EVANS, OF WATERTOWN, MASSACHUSETTS, ASSIGNOR T SIMPLEX WIRE AND CABLE COMPANY, 0F BOSTON, MASSACHUSETTS, A CORPORATION OF MASSACHUSETTS INSULATION O F WIRE Application led February 24, 1930. Serial No. 430,72-5.

This invention relates to improvements in the application of liquid dispersions of insulating materials to wire in the manufacture of insulated wire and cable. The invention includes improvements in process and in apparatus.

The invention is of special value in the application of aqueous dispersions including vulcanized but substantially uncoagulated rubber, such for example as are described 'have found that such liquid dispersions tend in United States Letters Patent Number 1,433,149 and 1,682,857, issued January 23rd,

1928, and September 4th, 1928, respectively,

to wire. In one aspect, this invention provides improvements of special value in carrying out the process and in making the product described in an application filed November 7th, 1928, by Charles R. Boggs, Serial Number 317,883.

Liquid dispersions, such as the aqueous dispersions of vulcanized but substantially uncoagulated rubber just mentioned, frequently become unstable when subjected directly to friction, local pressure or agitation produced by the coaction of mechanical elements within the liquid dispersions. For example, iny attempted application of such liquid dispersions to wire by passing the wire beneath a sheave positioned in a bath of the liquid dispersion, the common method of applying liquid coating materials to wire, diiiiculties are frequently encountered due to the formation of coagulated lumps or strings of the dispersed material in the bath, involving the production of a nonuniform and consequently unsatisfactory product. This tendency seems to be due to the coaction between the wire and the sheave or between the sheave and its mounting within the bath.

In endeavoringto eliminate these difficulties, I have devised a number of processes and various apparatus. For example, Ihave been able to apply such liquid dispersions to wire by passing the wire while suspended as a free loop through a bath of the liquid dispersion. Again for example, I have been able to apply such liquid dispersions to wire by arranging sheaves or other guides for the wire within a bath of mercury and floating a bath of 50 the liquid dispersion upon that part of this -sonous material and is subject to diiiioulties with respectto entrainment of mercury on the wire or in the applied coating.

In my study of this problem, however, I

to flow more readily over a surface previously wetted by the liquid dispersion than over a surface previously unwetted by the liquid dispersion, and I have embodied thisprinple in the process and apparatus of my present invention to secure a number of important practical advantages.

In carrying out the process of my present invention, I pass the wire, then imwetted by the liquid dispersion, upwardly through an aperture in a die somewhat larger than the wire and then through a pool of the liquid dispersion maintained on the upper face of the die without permitting the wire to contact with the die, and I prevent the liquid d1s persion from flowing downwardly along the dimensioning the aperture through the die so that it is smallest in section above its lower end and flares outwardly below this smallest section. I thus provide, in effect, for the entry of the wire into the lower part of the bath of the liquid dispersion, to be passed upwardly therethrough, without the use of stuiiingeboxes or sheaves or other mechanical elements coacting with each other or with the wire within the liquid dispersion. Part of the liquid dispersion flows downwardly through the aperture, through the space around the wire, but, unless the aperture through the die is so much larger than the wire as to permit this flow to be very rapid, this part of the liquid dispersion foli 40 iiii I position the die, having a vertical aperture therethrough smallest in section above its lower end and ilaring outwardly below said smallest section, above and in alignment with 5 a trap having a vertical aperture therethrough, the aperture through the trap being at least as large in section as the smallest section of the aperture through the die and being smaller in section at its upper end than the lower end of the aperture through the die,

and I position guides, sheaves for example, above the die and below the trap so that a wire moving upwardly through the trap and the f die over these guides is prevented from contacting with the die.

I will describe my invention in connection with the accompanying drawings which illustrate, somewhat diagrammatically and conventionally, apparatus embodying my invention and adapted for carrylng out my invention. It is intended and will\be understood that the accompanying drawings and the following more detailed description are for the purpose of exempliica- J tion; my invention can be carried out in apparatus other than that shown, and the apparatus can be changed and modified in many respects without departing from the spirit of my invention. In the accompanying drawings;

Fig. 1 is a front elevation of a. machine embodying my invention and adapted Afor carrying'out my invention,

' Fig. 2 is a side elevation of the same machine,

A drawings are shown in detail'ln Figs. 4 and 5. The die 6 has a vertical aperture therethrough which is smallest in section above itsv lower end and which liares outwardly belowr this smallest section to a substantially larger section -at its lower end. The trap 7, 'formed by the-extension of the annulus 8 within the lower end of the die chamber, has

a vertical aperture therethrough, aligned with the Aaperture through the die 6, at least as large in section throughoutl as the smallest section of the aperture through the die 6 55' and smaller in section at its upper end than the lower end of the aperture through the die 6. Liquid flowing downwardly through the aperture through the die 6, following the enlargement of the aperture, drops into the trap 7T- The liquid dispersion to be applied to the wire 9, passed upwardly through the die 6, is supplied through inlet 10 at a rate fast enough to maintain a pool ofvtheliquid dispersionl on the Lupper lface of the `die 6,

6.5 that part of the liquid dispersion flowing` in more detail through the aperture in the die 6 being discharged from ,the trap 7 through outlet- 11 and any excess being discharged from the pool through outlet 12. It Will be apparent that the pool of liquid maintained on the upper face of the die 6 is controlled by regulating the rate at which the liquid dispersion is supplied through inlet 10 and either or .both the rate at which the dispersion is discharged through outlet 12 or the position of outlet 12. A door- 13 is provided to aiord access to the die chamber and, to avoid discharge of the liquid dispersion through this door, guards-14 and 15 are provided on the die and guard 16 is pr vided in the trap.

The carrying out o my invention in this particular apparatus may be illustratedl by the following example: To apply an aqueous dispersion of vulcanized but substantially uncoagulated rubber having a viscosity of from 5 to 100 times the viscosity of water to wire up to 0.090 inches in diameter, the smallesty section of the aperture through the die 6 may be 0.160 inches in diameter and the wire may be passed through the die at a rate approximating 8 feet per minute.

After` the wire has passed through the bath of the liquid-dispersion of insulating mate- -rial to be applied to the wire, it is carried upwardly'for a distance great enough to aff ford the time necessary for drying of the applied coating before the coated wire is brought into contact with the guide above the die or any other mechanical element. This, of course, is conventional practice in the application of various coating materials to wire.

The liquid dispersion discharged throu l1 the outlets 11 and 12 may be returned to t e reservoir from which-the liquid dispersion is supplied through inlet 10 or this discharged liquid dispersionmay be sup lied to the next die chamber of a series o die chambers. A single application of the liquid dispersion may be sufficient in some cases lating material, several successive applica. tions of the liquid dispersion may be necessary. The machine illustrated in Figs. 1, 2 and 3 is arranged to subject the wireto 9 successive applications of the liquid dispersion of insulating material. v

or, to build up a'thicker layer of the insu- Referring more particularly ,to Figs. l.

2 and 3, the wire to be coated is suppliedV from a reel 17 and the coated wire is taken olf on a reel 18. Power is supplied `by the motor 19 through reduction gears and .a change gear set 20 to the counter shaft 21. The wire. from the supply 4'reel 17 passes around the capstan 22, through the tank 23 beneath the sheave 24, upwardly through the heater-drier`25 and over thesheave 26,

downwardly and over the first lower guide sheave 27, upwardly from this'- guide sheave 27 through the first; die chamberl 283 and through the heater-drier 25 and over the first upper guide sheave 29, downwardly and over the second lower guide sheave 27a, upwardly from this guide sheave 27a through the second die chamber 28a and through the heater-drier 25 and over the second upper guide sheave 29a, and so on through each of the successive die chambers in the series, from the last die chamber 28h upwardly through the heater-drier 25 and over the last upper guide sheave 29h, twice more through the heater-drier 25 over the lower sheaves 30 and the upper sheaves 31, and then to the take-olf reel 18 over the guide sheave 32 through the chalk hopper 33. The wire is carried through the machine by the capstan 22 and by a series of friction drives 34, 34a, etc., 34h, and 41, picking up the wire each time as it passes downwardly from the upper sheaves 26, 29, 29a, etc., and the sheaves 31, to the lower sheaves 27, 27a, etc., and 30. The series of friction drives 34, etc., and 41, are driven from the counter shaft by means of belt 35, the capstan 22 is driven from the friction drive shaft 3b through belt 37, and the take-off reel 18 is driven from the friction drive shaft 36 through traverse shaft 38. The liquid dispersions of insulating material are supplied to the inlet of the first die chamber 28 through connection 39, overflows and is discharged from the irst die chamber 28 to the second die chamber 28a and so on to the last die chamb-er 28h and overflows and is discharged from the last die chamber 28h through connection 40.

To the extent that the die chambers eX- tend upwardly above the surface of the pools of the liquid dispersion maintained on the upper face of the dies therein` an atmosphere of any volatile components of the liquid dispersion of insulating material is maintained, partially confined, above the pools of the liquid dispersion inhibiting evaporation of such volatile components from the liquid dispersion. If desirable for any reason, the die chambers can be elongated 'to secure this result in increasing measure.

The wire may be subjected to treatment with any desired treating or conditioning agents or preliminary coating materials in `the tank 23. For example, a paste may be applied to the wire as it passes through tank 23 to smooth out surface irregularities, or a paste may be Yapplied to a twisted pair or parallel pair ofwires to iill interstices. pretreatment is not part of my present invention.

My invention is useful in the application of liquid dispersions of insulating materials to bare wire and to wire previously covered with other insulation or protection, for example, to enamelled wire or to wire covered with cotton. invention is also useful in and said die oversaid guides to avoid contact the application of liquid dispersions of insulating materials to multi-conductor wire Such `and cable as primary insulation or as a jacket over other insulation, to individual conducting elements or to groups of conducting elements. My invention is useful in the application of liquid dispersions of various insulating materials including, for example, rubber, gutta percha, balata, vulcanized or unvulcanized, without or together with other compounding materials commonly used in insulation. My invention is, however, of special value in connectionwith the application of dispersions including vulcanized but substantially uncoagulated rubber, as noted above.

I claim:

1. In the application of coagulable liquid dispersions of insulating material to wire, the improvement which comprises passing the wire', then unwetted by the liquid dispersion, upwardly through an aperture substantially larger than the wire in a die and then through a mechanically undisturbed pool of the liquid dispersion maintained on the upper face of the die without permitting the wire to contact with the die, and causing the liquiddispersionflowingdownwardlythrough the aperture to be carried away from the approaching unwetted wire below said die.

2. In the application of coagulable aqueous dispersions of vulcanized but substantially uncoagulated rubber to wire, the improvement which comprises passing the wire, then unwetted by the aqueous dispersion of vulcanized but substantially uncoagulated rubber, upwardly through an aperture substantially larger than the wire in a.l die and then through a mechanically undisturbed pool of the aqueous dispersion of vulcanized but substantially uncoag'ulated rubber maintained on the upper face of the die without permitting the wire to contact with the die, and causing the aqueous'dispersion of vulcanized `but substantially uncoagulated rubber iowing downwardly through the aperture to be carried away from the approaching unwetted wire below said die.

3. Apparatus for applying liquid dispersions of insulating material to wire, comprising a die having a. `vertical aperture therethrough, said aperture being smallest in section above its lower end and flaring outwardly below said smallest section, a trap having a vertical aperture therethrough in alignment with said first-mentioned aperture positioned beneath said die, said second-mentione-d aperture being at least as large in section through out as said smallest section of said first-mentioned aperture, the upper end of said second-mentioned aperture being in section smaller than the lower end of said first-mentioned aperture, guides positioned above said between said wire and said die, means for maintaining a pool of the liquid dispersion of insulating material on the upper face of said die and means for discharging such liquid dispersion from said trap away from said Wne.

In testimony whereof I afx my signature.

VRALPHRUSSELL EVANS. 

